Ken,
There the best leds have ever been at producing a blanket of light but similar to t5 you are aiming to cover the whole of the waters surface with units to provide full coverage and minimal shading
Heat wise they run way cooler than halide
Currently running at around 40deg directly at the heat sink (which is the full foot print of the unit)
Cooled by 4 large fans per unit these are virtually silent even now
It’s 32deg outside and these are not making a sound
The old radion these replaced used to scream at 100% intensity!!!